Overview

Microsoft developed a full-featured scheduler for IE 4, IE 5, Win 98, and NT 5. From looking at all the task
options available (three property pages, plus an "advanced" dialog) you could imagine that programming
the scheduler is quite a chore. And you'd be right. I developed the CScheduledTask class to help you create very
simple tasks and understand the basics of using the scheduler.

There is plenty of room for improvement in this class. This was done purposely on my part -- making a class
to implement all the features of the scheduler would have amounted to rewriting the scheduler UI, which I really
didn't want to do (for free ). As it currently stands, CScheduledTask can create and delete events from
the scheduler. Tasks can have simple schedules, namely one time only, daily, weekly, or monthly.

CScheduledTask was written with MSVC 6.0 on Win 98. It should work OK in Unicode, although I haven't tested
it. I do use a couple of 6.0-specific functions, such as CTime::GetAsSystemTime() and CString::Delete(), so in
order to build with MSVC 5.0, you'd need to convert those sections back to use MFC 4.2 functions. You would also
need the INetSDK or Platform SDK installed, because you need to link with MSTASK.LIB for the scheduler GUIDs and
#include MSTASK.H for the interfaces.

Please note that this class does not interface with the AT service, the default scheduler on
NT 4 and earlier.

Creating a task

So, you want to schedule a program, eh? Here is the information you'll need to provide to CScheduledTask:

Program name: The fully-qualified path to the program (required).

Parameters: Any command-line parameters you want to pass to the program (optional).

Starting directory: The starting directory for the program (optional).

Account and password: The account the task will run under, and the account's password (required for NT only).

Starting date and time: The date and time a one-time task will run, or the beginning date and time for a repeating
task (required).

Ending date: The last day that a repeating task will run (optional, N/A for one-time tasks). If this is not
set for a repeating task, the task will repeat indefinitely.

Frequency: One time, daily, weekly, or monthly (required).

Comment: A string to be displayed in the task's property sheet in the scheduler UI (optional).

There's a little catch when creating a weekly repeating task: if you want the task to repeat on Mondays, the
starting date must be a Monday. Similarly, for monthly tasks, if you want the task to run on the 20th, the starting
date must be a 20th.

The CScheduledTask member functions for doing all this are listed below:

Note that there are two functions for setting the starting time, and two for the ending date. The two overloads
let you pass in a CTime or SYSTEMTIME, depending on whatever format you use in your code.

ETaskFrequency is an enumeration that has the following values:

enum ETaskFrequency
{
freqOnce, freqDaily, freqWeekly, freqMonthly
};

Once you've set all the relevant info, call the SaveTask() function:

HRESULT SaveTask ( LPCTSTR szTaskName, BOOL bFailIfExists = FALSE )

The return value is S_OK if the save was successful. If you call this function before setting a required parameter
(i.e., task name, start date/time, or frequency), the return value is E_FAIL. If a scheduler COM method fails,
the HRESULT returned is the error returned by the last COM method that was called. In the debug version, CScheduledTask
will display a trace message listing which method failed.

The bFailIfExists parameter determines if SaveTask() will bail out if a task with the given name already exists.
The default behavior is to replace an existing task.

Deleting a task

Deleting a task is quite easy - just call the DeleteTask function:

static HRESULT DeleteTask ( LPCTSTR szTaskName )

Note that this is a static function, and it works independently of everything else in the class. This function
also returns an HRESULT, similar to SaveTask().

Other functions

If you have the need to clear out the contents of a CScheduledTask object, call the Reset function:

void Reset();

I have also included accessor functions to return the various task parameters. They are:

These functions are there for the sake of completeness, they were easy to write, and they also provide a starting
point for future enhancements, such as the ability to enumerate through existing tasks in the scheduler.

GetStartDateTime() and GetEndDate() return a BOOL indicating if the corresponding date/time has been set. They
return TRUE if the date/time is set, or FALSE if not. GetFrequency() returns the special value freqUnset if no
frequency has been set. The remaining functions return an empty string if the corresponding item has not been set.
Note that there is no GetPassword() function, because the Task Scheduler API doesn't provide a way to retrieve
the password.

Updates

April 18, 1999: Version 1.1 has these changes:

Fixed some compile errors when building for Unicode. Thanks to Chris Maunder for providing the fixes!

Fixed SaveTask() to properly check for an existing task. The change was necessary because I worked around a
bug in IE 4, but the bug was fixed in IE 5, resulting in my code breaking when run on IE 5.

Added a #pragma to automatically link with mstask.lib, so you don't have to remember to do that in
your app's project settings.

Added a check after the CoCreateInstance() call to see if the error is REGDB_E_CLASSNOTREG. If so, I display
a nicer trace message explaining that you don't have the scheduler installed.

November 27, 1999: Version 1.2 has these changes:

Added functions to set an account and password for a task, so the task will run on NT.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Michael lives in sunny Mountain View, California. He started programming with an Apple //e in 4th grade, graduated from UCLA with a math degree in 1994, and immediately landed a job as a QA engineer at Symantec, working on the Norton AntiVirus team. He pretty much taught himself Windows and MFC programming, and in 1999 he designed and coded a new interface for Norton AntiVirus 2000.
Mike has been a a developer at Napster and at his own lil' startup, Zabersoft, a development company he co-founded with offices in Los Angeles and Odense, Denmark. Mike is now a senior engineer at VMware.

He also enjoys his hobbies of playing pinball, bike riding, photography, and Domion on Friday nights (current favorite combo: Village + double Pirate Ship). He would get his own snooker table too if they weren't so darn big! He is also sad that he's forgotten the languages he's studied: French, Mandarin Chinese, and Japanese.

I have previously downloaded the sample project, and library from the same site, everything that we can do with a task is available with this dll. But the only thing is I am able to play with taskflag to disable(only and not enable) for the task which is scheduled. I searched on various sites and also hexcodes for a scheduled task, but i could not find the hexcode for disable or enable the scheduled task. Finally, from MSDN I came to know that if I want to enable or disable a scheduled task with code in vb.net or c#.net what I need is "Vista" or MS win 2008 server. Isn't there any other magic that will help me to enable/disable a scheduled task with vb.net on MS 2000 Advanced server and MS .Net 2005 ????

Can we create tasks that are not visible to the user so that the user cannot disable them?
I tried out the flag "TASK_FLAG_HIDDEN", but that did not work! Task was created successfully but it did not execute.

But you can do that, provided you know the correct User Credentials and have appropriate rights to run your malware.
I even tried at that. ..just to test.But one problem: You have scheduled a task with the current user's password, what if the user changes his password before the task being executed?

"We assume you already know not to consider something like Windows as a firewall platform. Does the name "Windows" evoke images of security? Silly rabbit, Windows is for desktops." -- Unix System Administration Handbook